Cloud Point Extraction Procedure for the Determination of Mercury by Spectrophotometry Using a New Synthesized Ligand

Abstract

A new thiazolylazo reagent was prepared and exploited for the cloud point extraction
(CPE) methodology in the preconcentration of micro amount of Hg (II) as a prior step to its
determination by UV-Vis spectrophotometry. The extraction and determination processes of
Hg(II) involved the complexation of Hg (II) with synthesized 7-(6-Bromo 2-benzothiazolyl
azo)-8-Hydroxyquinoline (7- (6-BrBTA8HQ) at specific pH which is extracted by micelles of
the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and subsequently
detected spectrophotometrically at specific 640 nm. The optimal reaction and extraction
conditions (e.g. pH, reagent concentration, surfactant concentration, equilibrium temperature
and the incubation time) were studied and the analytical figures of merit of the method (e.g.
linearity, limit of detection, sensitivity, enrichment factor etc) were obtained. The
interferences effect of the foreigner metal ions was also considered. Under the optimum
established conditions, the enrichment factor of 123 folds was achieved which led to a
detection limit of 7.4 ng mL-1 of Hg (II) and concentration range of 8-500 ng mL-1 with
percent recovery of 100.43±1.23. The precision for seven replicate measurements of 200 ng
mL-1 Hg (II) was of 0.67%. The method was applied to the determination of mercury in some
fish samples with satisfactory results.